Apparatus for conveying bulk material between areas under different gas pressures

ABSTRACT

Bulk material conveying apparatus includes a tubular element connected between hoppers under different gas pressures. A rotary helical conveying worm extends through a portion of the tubular element to feed bulk material from one of the hoppers through the tubular element to the other hopper, the conveying worm compressing the bulk material to form a plug in the tubular element downstream from the end of the conveying worm to prevent flow of gas between the two hoppers. Gas pressure sensing means is provided for detecting any changes in pressure in one of the hoppers to control adjustment of the conveying worm in an axial direction in the tubular element whereby the size of the plug can be increased or decreased as necessary to maintain a predetermined pressure in the hopper.

ilnited States Patent m1 Teslkc 1 1 Sept. 4, 1973 [54] APPARATUS FORCONVEYING BULK 2,681,610 6/1954 Schrock 198/213 X MATERIAL BETWEEN AREASUNDER 3,345,?83 $136: 1lsiolkin 214/17 B X DIFFERENT GAS PRESSURES ,60 57 organ 198/213 X [75] inventor: Lothar Teske, Porz-Westhoven, FOREIGNPATENTS OR APPLICATIONS Germany 1,209,061 1/1966 Germany 214 17 81,180,083 6/1959 France 214/17 B [73] Assignee: Maschinenbau LouiseGmbH, 1,243,885 9/1960 France 1 302/50 Westhoven, Germany 615,779 5/1933Germany 1 302/50 686,718 1/1953 Great Britain 302/50 [22] Flled: July16, 1971 21 App| 163,1 3 Primary Examiner-Robert S. Ward, Jr.

Attorney-Markva & Smith [30] Foreign Application Priority Data [57]ABSTRACT May 12, 1971 Great Britain 14,572/71 Bulk material conveyingapparatus includes a tubular element connected between hoppers underdifferent [52] US. Cl. 214/17 B, 222/55, 2232421532), gas pressures Arotary helical conveying worm extends through a portion of the tubularelement to feed bulk [51] int. Cl 865g 65/30, B67d 5/03 material fromone of the hoppers through the tubular [58] Field 01' Search 222/55,413, 409, element to the other hopper, the conveying worm 141/67 214/17198/64 302/50 pressing the bulk material to form a plug in the tubularelement downstream from the end of the conveying [56] References cuedworm to prevent flow of gas between the two hoppers. UNITED STATESPATENTS Gas pressure sensing means is provided for detecting 1,737,09011/1929 Meyers 214/17 B any changes in pressure in one of the hoppers tocon- 1,941,573 H1934 MOI'IOW 302/50 trol adjustment of the conveyingworm in an axial di- 1 9/1935 214/17 B rection in the tubular elementwhereby the size of the 3 32 31 5 2; g f plug can be increased ordecreased as necessary to avls 2,374,363 4 1945 McCaskell 222/55 x apredetermmed pressure Mppe" 2,376,139 5/1945 Hemminger 214/17 B X 8Claims, 2 Drawing Figures PATENTEU E 3,756,434

SHEET 2 BF 2 FIG. 2

IN VEN TOR Aer/m 755m;

BY y HWAIYEVS' APPARATUS FOR CONVEYING BULK MATERIAL BETWEEN AREAS UNDERDIFFERENT GAS PRESSURES This invention relates to an apparatus forconveying bulk material between two areas which are maintained atdifferent gas pressures.

More specifically, the present invention relates to apparatus fortransferring bulk material from one container such as a bunker which isunder a positive or negative gas pressure to another containermaintained under a different positive or negative pressure. A primaryproblem in transferring bulk material between containers maintained atdifferent pressures is the prevention of gas flow between the containersthrough the conduit means used for transferring the bulk materialbetween the containers.

Prior art devices designed to transfer bulk material between containersmaintained at different pressures have included means for providing anair lock in the conduit used to transfer the bulk material. A rotatablydriven conveying worm extends a part of the distance through the conduitand a pivoted flap is biased towards a sealing position against thedownstream end of the conduit. With this arrangement, the conveying wormfeeds bulk material from one container into the conduit to form a plugin the conduit downstream from the end of the conveying worm, the plugbeing continuously pushed by further bulk material fed into the conduitagainst the flap at the opposite end of the tubular element as it isforced into the other container. It will be appreciated that the plug isintended to serve as an air lock to prevent gas flow between thecontainers through the conduit.

A disadvantage of the prior art devicesof this type is that theefficiency of the plug as an air lock to prevent gas flow depends uponthe consistency of the bulk material and also upon the differencebetween the pressures in the respective containers. It has been foundthat some bulk materials are easily compressed and in fact form acake-type plug. Other bulk materials which are usually free-flowing aredifficult to compress in the form of a plug. Furthermore, theconsistency of any particular bulk material will vary so that a constantseal obtained by the plug will not be maintained. The prior art deviceshave provided no means for compensating for the variations in theconsistency of the bulk material to maintain a constant pressure in oneor both of the containers.

It is an object of the present invention to provide an improvedconveying means for bulk material wherein the efficiency of the air lockmay be maintained irrespective of the consistency of the bulk material.

It is a further object of the invention to provide conveying apparatuswherein the length of the plug formed in the conduit may be varieddepending upon the consistency of the bulk material being conveyed.

It is a still further object of this invention to provide an improvedconveying means wherein adjustment is automatically made in the lengthof the plug in the conduit responsive to fluctuations in gas pressure inone of the containers.

Briefly, the present invention comprises a prior art apparatus of thetype described above, but means is provided for moving the conveyingworm axially so that the distance between the end of the conveying wormand the outlet end of the conduit may be correspondingly varied. It willbe appreciated that with this arrangement the length of the plug in theconduit may be varied. In a preferred embodiment of the invention, gaspressure detecting means is provided for detecting fluctuations inpressure in one of the containers, and further means is providedresponsive to the pressure detecting means for moving the conveying wormaxially to change the length of the plug as necessary.

When the consistency of the bulk material is such that it will notcompress easily, the conveying worm is moved in an axial direction toincrease the length of the plug to form an airtight seal in the conduit.Conversely, if the bulk material can be compressed easily, a shorterplug is desirable; and therefore the conveying worm is moved axially inthe opposite direction. It is undesirable for the plug length in theconduit to be unnecessarily long, since the power required to force thepacked bulk material through the conduit may become excessive. If thebulk material packs easily and forms a cakelike plug, the power requiredto rotate the conveying worm will be increased; and if increased poweris not available, the delivery rate for the bulk material will bedecreased substantially, since proper rotational speed for the conveyingworm cannot be maintained. It is therefore desirable to provideautomatic pressure detecting means to control the position of theconveying worm in the conduit and thereby control the length of the plugso that a minimum plug length will always be maintained consistent withthe maintenance of a gastight seal in the conduit.

The present invention is extremely desirable where a reliable seal isnecessary to prevent toxic gases from flowing out of a container duringremoval of bulk material. This type of apparatus is also desirable inpreventing the inflow of oxygen under certain circumstances which mightgive rise to the danger of explosions.

In order that the invention may be understood, reference will now bemade to the drawing wherein an exemplary embodiment is shown. It isunderstood that variations may be made without departing from the scopeof the invention as defined by the appended claims.

FIG. I is a side view partly in section of the bulk loading/unloadingapparatus; and

FIG. 2 is a plan view of the apparatus of FIG. I.

In the embodiment shown, the loading/unloading apparatus isarranged totransfer bulk material 28 from bunker 1 which is maintained at apressure P to a second bunker 2 maintained at a different pressure P,.An air lock head 12 is connected to the top of bunker 2 by flange l5 andincludes a scalable aperture 16 and a front discharge aperture 6. Adelivery pipe 4 extends horizontally from the front discharge aperture 6to a housing 20 and contains a conveying worm 5 for transporting thebulk material along the delivery pipe 4 towards the air lock head 12. Aunion 7 communicates with the delivery pipe 4 above the conveying worm 5to join the bottom of bunker 1 with the delivery pipe 4.

The front discharge aperture 6 is normally closed by a cover 8 tomaintain a substantially air-tight seal. The cover 8 is secured througha universal joint 10 to one end of lever 9 while the opposite end of thelever 9 is mounted on rotatable shaft 11. The shaft 11 extendshorizontally through the side wall of the air lock head 12 and an arm 14is secured to the end of the shaft 11. A weight 13 is arranged to belongitudinally displaceable on the arm 14 and to be secured at anylocation along the arm. Thus, the cover 8 is biased towards the frontdischarge aperture 6 to seal the aperture and the amount of bias can bevaried depending upon the distance of the weight 13 on arm 14 from theshaft 11.

The worm shaft 17 passes from the delivery pipe 4 through stuffing box18 in housing 20 and through a pair of bearings 19. The shaft of adriving motor 21 is operatively connected to the end of the worm shaft17 through coupling 36.

The pair of bearings 19 and the driving motor 21 are mounted on a commonlongitudinally displaceable plate 22 whereby the unit 26 which includesthe longitudinally displaceable plate 22, driving motor 21, coupling 36,the pair of bearings 19 and the worm shaft 17 including the conveyingworm can be moved longitudinally in either direction. Thus, theconveying worm 5 can be moved in either direction through the deliverypipe 4 while it is simultaneously being rotatably driven by motor 21.The longitudinal displacement of the plate 22 is controlled by adjustingmotor 23 which drives an externally threaded spindle 24 passing throughan internally threaded nut 25 secured to the plate 22. The adjustingmotor 23 is capable of being driven in either the forward or reversedirections for adjustment of the plate 22 and the conveying worm 5 ineither longitudinal direction.

A pressure measuring device 27 is located in the wall of air lock head12 for monitoring the pressure within bunker 2 which of course iseffected by the amount of gas which may pass between the two bunkersthrough the delivery pipe 4. Rotation of the conveying worm 5 driven bymotor 21 causes the bulk material 28 passing downwardly from the bunker1 through the union 7 to be conveyed forwardly (to the left as viewed inFIG. 1) through the delivery pipe 4 and to be compressed to form a plug30 between the end of the conveying worm 5 and the biased cover 8. Theeffectiveness of the plug 30 as an air lock to prevent air passagebetween bunkers l and 2 depends to a great extent upon the nature of thebulk material 28. A relatively short plug 30 is required where the bulkmaterial is easily compressed. On the other hand, if the bulk materialis not easily compressed, a substantially larger plug 30 will berequired to obtain an equally effective air lock. When there is anundesirable rise or fall of air pressure in bunker 2, the pressuremeasuring device 27 transmits a signal through control circuits 31 and33 and electrical transmission device 32 to actuate the adjusting motor23. If the pressure in bunker 2 either increases or decreased above orbelow certain predetermined limits, these fluctuations will be sensed bythe pressure monitoring device 27 and a signal will be transmitted tothe adjusting motor 23 causing the longitudinally displaceable plate 22and the conveying worm 5 to be moved forwardly or rearwardly as requiredto decrease or increase, respectively, the length of plug 30 in deliverypipe 4. The distance between the front discharge aperture 6 and theunion 7 at the bottom of the bunker l is sufficiently great so that inno event will the end of the conveying worm 5 when moved rearwardlyreach the location of the union 7 on the delivery pipe 4.

The motor 21 continues to drive the conveying worm 5 during movement ofthe longitudinally displaceable plate 22 by the adjusting motor 23.However, a further control circuit 34 leads from the adjusting motor 23to the driving motor 21 for transmitting a signal by way of an amplifierdevice 35 which signal is dependent upon the direction of rotation ofthe adjusting motor 23. The signal causes the rotational speed of themotor 21 to be increased or decreased as required.

The control system permits the bulk material plug 30 to be continuouslyincreased or reduced in length depending upon the pressure in bunker 2as sensed by the pressure monitoring device 27. The result is themaintenance of a substantially constant pressure in bunker 2irrespective of the nature of the bulk material 28 and its ability to becompressed and to serve as a plug. At the same time, the least possibleload is placed on the driving motor 2] consistent with the maintenanceof a maximum sealing effect. When the plug is required to be increasedin length, the rotational speed of the driving motor is correspondinglyincreased to compensate for this greater length and conversely as thesealing plug 30 is reduced in length, the rotational speed of thedriving motor 21 is reduced.

It will be appreciated the above described automatic adjusting means forboth controlling the length of the bulk material plug and the rotationalspeed of the conveyor worm can also be manually regulated on the basisof readings taken from a pressure gauge substituted for the pressuremonitoring device. Furthermore, it will be appreciated that though anarrangement has been described in which the pressure in bunker 2 servesto control the apparatus, the pressure measuring device can be arrangedto sense fluctuations in pressure in bunker 1 and to control theapparatus in the same manner.

1 claim:

1. Apparatus for conveying bulk material along a path between areashaving different gas pressures while minimizing the flow of gas alongsaid path between said areas comprising a. conduit means having inletand outlet ends and extending between said two areas,

b. means extending into the inlet end and a part of the distance throughsaid conduit means for feeding said bulk material from one of said areasinto the inlet end of said conduit means, for compressing said bulkmaterial in said conduit means to form a gas-tight plug downstream fromsaid feed means, and for pushing said plug along said conduit means andthrough the outlet end of said conduit means into the other of saidareas,

0. means for adjusting the distance said feed means extends through saidconduit means, and

d. means for sensing the gas pressure in one of said areas and forregulating said adjusting means,

e. whereby the length of said plug in said conduit means between the endof said feed means and said outlet end may be adjusted and maintained ata minimum length required to maintain its effectiveness in minimizingflow of gas depending upon the degree of difference in gas pressurebetween the two areas and the consistency of the bulk material.

2. Apparatus as defined in claim 1 wherein said conduit means comprisesa tubular element and said feed means comprises a rotary helicalconveying worm, said adjusting means comprising means for moving saidconveying worm in either direction along its axis.

3. Apparatus as defined in claim 1 further comprising means for sealingthe outlet end of said conduit means adjacent the other of said areas,means mounting said sealing means for movement towards and away from asealing position, and means biasing said sealing means towards saidsealing position whereby the formed plug in said conduit means will movesaid sealing means away from said sealing position when said plug passesthrough said outlet into the other of said areas.

4. Apparatus as defined in claim 1 further comprising a first gas-tighthopper communicating with the outlet end of said conduit means forreceiving said bulk material and a second gas-tight hopper communicatingwith the inlet end of said conduit means for retaining bulk material tobe fed through said conduit means into said first gas-tight hopper.

5. Apparatus as defined in claim 2 further comprising drive means forrotating said conveying worm and means responsive to said pressuresensing means for controlling the rate of rotation of said conveyingworm whereby the bulk material is continuously compressed to form saidplug, the rotational speed of said conveying worm being increased whenmoved away from said outlet end and decreased when moved towards saidoutlet end.

6. Apparatus according to claim 2 further comprising means for rotatablysupporting said conveying wonn, said means for moving said worm alongsaid axis comprising means for moving said support means parallel tosaid axis.

7. Apparatus as defined in claim 2 wherein said pressure sensing meansis adapted to sense the pressure in the area at the outlet end of saidtubular element.

8. Apparatus as defined in claim 3 wherein said sealing means comprisesa closure flap, means pivotally mounting said closure flap andadjustable weight means of adjusting the amount of bias applied to theclosure flap in the direction of said outlet end of the conduit

1. Apparatus for conveying bulk material along a path between areashaving different gas pressures while minimizing the flow of gas alongsaid path between said areas comprising a. conduit means having inletand outlet ends and extending between said two areas, b. means extendinginto the inlet end and a part of the distance through said conduit meansfor feeding said bulk material from one of said areas into the inlet endof said conduit means, for compressing said bulk material in saidconduit means to form a gas-tight plug downstream from said feed means,and for pushing said plug along said conduit means and through theoutlet end of said conduit means into the other of said areas, c. meansfor adjusting the distance said feed means extends through said conduitmeans, and d. means for sensing the gas pressure in one of said areasand for regulating said adjusting means, e. whereby the length of saidplug in said conduit means between the end of said feed means and saidoutlet end may be adjusted and maintained at a minimum length requiredto maintain its effectiveness in minimizing flow of gas depending uponthe degree of difference in gas pressure between the two areas and theconsistency of the bulk material.
 2. Apparatus as defined in claim 1wherein said conduit means comprises a tubular element and said feedmeans comprises a rotary helical conveying worm, said adjusting meanscomprising means for moving said conveying worm in either directionalong its axis.
 3. Apparatus as defined in claim 1 further comprisingmeans for sealing the outlet end of said conduit means adjacent theother of said areas, means mounting said sealing means for movementtowards and away from a sealing position, and means biasing said sealingmeans towards said sealing position whereby the formed plug in saidconduit means will move said sealing means away from said sealingposition when said plug passes through said outlet into the other ofsaid areas.
 4. Apparatus as defined in claim 1 further comprising afirst gas-tight hopper communicating with the outlet end of said conduitmeans for receiving said bulk material and a second gas-tight hoppercommunicating with the inlet end of said conduit means for retainingbulk material to be fed through said conduit means into said firstgas-tight hopper.
 5. Apparatus as defined in claim 2 further comprisingdrive means for rotating said conveying worm and means responsive tosaid pressure sensing means for controlling the rate of rotation of saidconveying worm whereby the bulk material is continuously compressed toform said plug, the rotational speed of said conveying worm beingincreased when moved away from said outlet end and decreased when movedtowards said outlet end.
 6. Apparatus according to claim 2 furthercomprising means for rotatably supporting said conveying worm, saidmeans for moving said worm along said axis comprising means for movingsaid support means parallel to said axis.
 7. Apparatus as defined inclaim 2 wherein said pressure sensing means is adapted to sense thepressure in the area at the outlet end of said tubular element. 8.Apparatus as defined in claim 3 wherein said sealing means comprises aclosure flap, means pivotally mounting said closure flap and adjustableweight means of adjusting the amount of bias applied to the closure flapin the direction of said outlet end of the conduit means.